Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Tuesday, March 29, 2011

- PVSJ 563 was listed as a paratype, but this is a typo (Sereno, pers. comm.).

- Eodromaeus specimens were thought to be Eoraptor until 2000, but Sereno (pers. comm.) confirms there are indeed several specimens besides the holotype correctly referred to Eoraptor that await description.

- Several of Eodromaeus' listed autapomorphies are shared with Herrerasaurus, such as the ventrally convex maxillary alveolar margin (more poorly developed in Sanjuansaurus), large distal carpal 5 overlapping distal carpal 4 with a posteroventral heel (note Sereno misidentified carpal 5 as 4 in 1993- Ezcurra, 2010), and pubic apron with sinuous lateral margin (in Sanjuansaurus too, but not developed much in Staurikosaurus). Of course Eodromaeus specimens are adult so it's not a synonym, but these might be saurischian/theropod plesiomorphies.

- The supposed small herrerasaurid forelimb MACN-PV 18.649a mentioned by Ezcurra and Novas (2007, 2008) may be referrable to Eodromaeus. It was referred to Herrerasauridae due to- enlarged distal carpal V; manual phalanx I-1 longer than metacarpal I; strongly curved manual unguals; metacarpals IV-V ventral to the others. All of these are present in Eodromaeus as well. Ezcurra (2010) states that it differs from Herrerasaurus in having manual phalanx II-1 with a conspicuous longitudinal ridge on its proximolateral border. Eodromaeus does have a marked proximolateral projection on II-1, but whether this is a ridge or not is not described. Ezcurra's (2010) matrix could be checked for further information on the forelimb's morphology, which could then be compared to Eodromaeus.

- In Martinez et al.'s (2011) cladogram, Tawa is the basalmost coelophysoid. In this case, Avepoda contains Tawa and other coelophysoids under ACCTRAN character optimization, but excludes Coelophysoidea under DELTRAN optimization. Gotta love apomorphy-based definitions...

Ezcurra, 2010. A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: A reassessment of dinosaur origin and phylogeny. Journal of Systematic Palaeontology. 8(3), 371-425.

Monday, March 28, 2011

When Eodromaeus was described, much was said about the analysis placing Eoraptor in Sauropodomorpha. What nobody did was elaborate on why Martinez et al. (2011) placed it there and how strong the evidence is. So I made a NEXUS file from Martinez et al.'s matrix to extract the character evidence.

The first thing to note is that the characters listed as multistate don't correspond to those with more than two states in the matrix, which also means the characters said to be ordered aren't those that should be. So I ordered 51, 69, 70, 76 (though nothing is coded with state 2, making ordering useless), 102 and 117. In addition, the definitions of some multistate characters have problems. "Premaxillary tooth number: 4 (0); 3 (1); 5 or 6 (2)" should ideally be ordered, but states 0 and 1 need to be switched so that the intermediate state is in the middle. "Maxillary/dentary crowns, shape: recurved (0); subtriangular (1); lanceolate (2)" artificially separates the morphology of sauropodomorph and ornithischian teeth, which are after all both triangular and lanceolate in both clades. The current coding doesn't let the reduced curvature group them together. "Ilium, preacetabular process, shape: tab-shaped (0); strap-shaped (1); subtriangular (2); semicircular (3)" is problematic since the next character deals with preacetabular length, and the only difference between "strap-shaped" and the other choices is length. "Ilium, bevis[sic] fossa, shape and orientation: broad laterally-open depression (0); shallow groove or absent (1); arched ventrally-opening ovate or parallel-sided depression (2); arched ventrally-opening posteriorly-expanding to a width approximately 50% of its length (3)" combines a lot of independant variables. There's depth (already partly covered by another character), orientation, proportional width and posterior expansion. Oddly, lagerpetonids and Marasuchus are coded inapplicable, despite their correct state of "absent" being covered by state 1. So given those issues, I ran the matrix and found similar results to Martinez et al.- 3 MPTs of 247 steps each, CI of .615 compared to his 3 MPTs 246 steps each with a CI of .618. The topology is identical. If you don't constrain the outgroups to be in the order (hypothetical(Lagerpetonidae(Marasuchus(Silesauridae,ingroup)))), then you get a lot more trees, sometimes with non-dinosauriform sauropodomorphs, and/or ornithischian silesaurids and/or Marasuchus, presumably because characters supporting more basal nodes weren't included.

So that's the matrix, but what about Eoraptor's sauropodomorph position? It's supported by the following characters-

2. external naris size large, expanded narial margin.
The plesiomorphic state specifies a tapered snout, but some taxa coded 0 like Herrerasaurus, Eodromaeus and Ceratosaurus certainly don't have tapered snouts. If you measure Eoraptor's naris compared to its skull length, then yes it looks large. But that's because it has a short snout. If you measure naris length compared to some more neutral value such as skull height at the orbit, its naris is actually smaller than any other taxon in the matrix. Also, Panphagia does not preserve a premaxilla, so cannot be coded, contra the matrix.

19. nasal posterolateral process present.
This is actually unknown in silesaurids and Tawa (Nesbitt et al., 2009), though Panphagia has it (Martinez and Alcober, 2009). It is also present in Coelophysis (Downs, 2000), Megapnosaurus (Downs, 2000) and "M." kayentakatae (Tykoski, 1998).

45. dentary tooth 1 inset.
Oddly, silesaurids are coded as inapplicable, even though this is one of their distinctive characters. If anything ornithischians should be coded unknown, in case their predentary is homologous to the anterior dentary.

43. maxillary and dentary crowns lanceolate.
As noted above, there's no difference between Martinez et al.'s triangular and lanceolate shapes, as can be seen by the near identical shape of the supposed triangular tooth of Silesaurus (Dzik, 2003 fig. 5H) and the supposed lanceolate tooth of Panphagia (Martinez and Alcober, 2006 fig. 5B).

69. deltopectoral crest 45% or more of humeral length.Eoraptor's crest has previously been reported to be 35% of humeral length (Langer and Benton, 2006). Note that in this and other cases where I claim Martinez et al.'s codings for Eoraptor are incorrect, it's with the caveat that they are redescribing the taxon and may be shown to be right with the publication of their monograph. Genasaurs' should be polymorphic, since Scutellosaurus (Colbert, 1964) has a short crest. Ceratosaurus also has a short crest (Galton, 1982).

88. brevis fossa an arched ventrally-opening ovate or parallel-sided depression.
This was discussed above as being a composite character and miscoded in the outgroup (also in Staurikosaurus- Bittencourt and Kellner, 2009). Regardless, Eodromaeus has the same state as Eoraptor, so the combination is not unexpected in a basal theropod.

When all of the above are changed in the matrix, Eoraptor is the basalmost theropod. An additional question to ask is how many previously suggested theropod characters of Eoraptor are in the matrix? In particular, how many of the characters suggested to link it with Tawa+Avepoda are included? As listed in the Database, the previously suggested characters are as follows. Those included in Martinez et al.'s matrix are in bold.

Tykoski (2005)- subnarial process of premaxilla narrow and rod-like; maxilla anterodorsally concave; nasal contacts antorbital fossa; lacrimal inverted L-shape; lacrimal at least equal to orbital height and reaches orbit's ventral rim; antorbital fossa exposure on lacrimal large, with triangular fossa on ventral process;vertebra 25 (dorsosacral) incorporated into sacrum (not actually present in Eoraptor, contra Tykoski); humerus twisted; metacarpal I distal condyles strongly asymmetrical; preacetabular process thin and blade-like; postacetabular process longer than acetabulum (not actually present in Eoraptor- Ezcurra, 2010); pubic fenestra (incorrectly coded absent in Eoraptor); distal ischium <3 times minimum width of shaft; subrectangular distal tibia with posterolateral extension (incorrectly coded absent in Eoraptor).
Ezcurra (2006)- lateral surface of premaxillary body pierced by a single neurovascular foramina above the second premaxillary tooth; maxillary antorbital fossa rostral to internal antorbital fenestra broad and rostrocaudally well extended; medial wall of the antorbital fossa extends through the entire ventral border of the internal antorbital fenestra as a very narrow lamina; lateral lamina of bone of the lacrimal with no interruption of the lacrimal antorbital fossa and restricted to the caudal margin of the ventral ramus along its dorsoventral extension; rostral process of jugal excluded from the internal antorbital fenestra, bluntly squared rostrally; ventral process of the squamosal length forms more than half of the caudal border of the infratemporal fenestra (absent in Eoraptor); humerus length subequal or shorter than 0.6 of the length of the femur; extensor pits on the dorsal surface of the distal end of metacarpals deep, well developed; shaft of metacarpal IV in relation to that of metacarpals I-III significantly narrower (incorrectly coded absent in Eoraptor); metacarpal IV and fourth digit: proximal portion set lateral to Mc III (idem Mc V) and with only one or lacking phalanges; supraacetabular crest and lateroventral border of the postacetabular process (lateral brevis shelf) continuous as a weakly developed ridge; cnemial crest on proximal tibia moderately developed; caudal cleft between medial part of the proximal end of the tibia and fibular condyle present.
Nesbitt et al. (2009)- premaxilla-maxilla, subnarial gap between the elements (absent in Eoraptor); nasal possesses a posterolateral process that envelops part of the anterior ramus of the lacrimal; ilium, ischiadic peduncle orientation well expanded posteriorly to the anterior margin of the postacetabular embayment.
Ezcurra (2010)- posterior part of premaxillary alveolar margin edentelous, resulting in an interruption of the upper tooth row (absent in Eoraptor); anterior margin of maxillary antorbital fossa squared; dorsoventrally compressed ridge on lateral surface of maxilla, forming the ventral border of the antorbital fossa (alveolar ridge) (incorrectly coded absent in Eoraptor); orientation of the lacrimal orbital margin erect and close to vertical; supraacetabular crest of ilium flares lateroventrally to form a hood-like overhang that hides anterodorsal half of acetabulum in lateral view (coded absent in Eoraptor); well developed brevis fossa with sharp margins on the ventral surface of the postacetabular process of the ilium present, being directly ventrally facing; well developed tibiofibular crest on distal femur.

Of course some of these are only supportive of a theropodan Eoraptor given the proper outgroup/ingroup arrangement and some are absent in Eoraptor, showing their own matrices have problems. But of the 31 characters present (as far as I can tell) in Eoraptor, only 11 are included, and of those 11 at least 4 are incorrectly coded as absent. Enforcing a placement for Eoraptor closer to avepods than herrerasaurids in this modified matrix is 13 steps longer, but the you have to wonder how many of the proposed characters for placing Eoraptor outside Herrerasaurus+Avepoda were included and how correctly they are coded. It's all outside the scope of this post.

In the end, I don't think the evidence for placing Eoraptor in Sauropodomorpha is strong. Of the 12 characters, 4 seem absent in Eoraptor, 2-3 of the others seem present basally in avepods, 3 of the others are present in Herrerasaurus, and all have high homoplasy. Even the toothless dentary tip and lanceolate teeth are complicated by their presence in silesaurids and/or ornithischians. With so much homoplasy among basal dinosauromorphs, it's necessary to include fragmentary but important taxa like Lewisuchus, Guaibasaurus, Chindesaurus and Pisanosaurus. Only then and when we incorporate all suggested conflicting character data can we hope to have meaningful results.

Monday, March 21, 2011

The Sauropodomorph Database is almost ready to debut, but first here's a couple more entries to illustrate why I'm making the website. The first is "Yibinosaurus", whose usual online information is limited to what Olshevsky wrote on the DML in 2001. The other is "Sugiyamasaurus", which no one seems to have connected to Fukuititan yet.

"Yibinosaurus" Ouyang vide anonymous, 2001"Y. zhoui" Ouyang vide anonymous, 2001Toarcian, Early Jurassic
Dongyuemiao Member of Ziliujing Formation, Sichuan, China
Material- (Chongqing Museum of Natural History coll.) specimen including dorsal vertebraeComments- This name originally appeared in a guidebook, with the taxon stated to be under study by Ouyang. Ouyang (2003) later mentioned it in his thesis as a new genus, which he places in an eponymous subfamily within Vulcanodontidae. As he also includes the more basal Gongxianosaurus in Vulcanodontidae, Ouyang's conception of the family may be more of a grade. Ouyang further notes the anterior dorsal neural spines are transversely expanded, which he believes indicates a possible relationship to taxa with bifurcated spines like Datousaurus. As Ouyang states "Yibinosaurus" is from the same locality as Gongxianosaurus, the dorsal vertebrae, 51 articulated caudal vertebrae, scapulae and ilium mentioned by Luo and Wang (1999) as Gongxianosaurus sp. nov. may be the "Yibinosaurus" material. References- Luo and Wang, 1999. New discovery on dinosaur fossils from Early Jurassic, Sichuan, China. Chinese Science Bulletin. 44(23), 2182-2188.
Anonymous, 2001. Dinosaur Fossils from Chongqing Natural History Museum.
Ouyang, 2003. Skeletal characteristics of Mamenchisaurus youngi and the systematics of mamenchisuarids. PhD thesis. Chengdu University of Technology. 176 pp.

Saturday, March 19, 2011

The first step to starting your own analysis is compiling the data from past analyses. Here's all of the quantitative cladistic sauropodomorph analyses I know of, in chronological order, with the subsequent modifications listed indented afterwards. Ones I don't have copies of are in bold. If anyone has them, I'd be thankful for a pdf of course. A 'u' in front of the entry means the supporting matrix was not presented. Also, if there are any I missed, I'd love to know.

Thursday, March 17, 2011

This won't be a surprise to you who have followed my Zhao posts, but the Theropod Database is expanding. When I started the website back in 2004, Mike Keesey's Dinosauricon 2 was in the works so I didn't plan to cover other groups. But now there's really nowhere to go that has consolidated info on dinosaur taxa, e.g. if you wanted to find somphospondylan synapomorphies, a list of all Early Jurassic sauropods, or a material list for every taxon (well, Paleofile has the latter, but costs money). I've been keeping a basic list on my computer all these years, but it's time to update it and put it online. As with the ex-theropod portion of the site, it holds special interest for me because I'm unfamiliar with most of the data. It's also interesting because I'll be creating a sauropodomorph matrix to analyze all the taxa. Most valid Mesozoic theropod taxa have been included in at least one analysis, but I don't think that's true for sauropods, especially the many titanosaurs and basal camarasauromorphs. Nor have most actually been compared to each other, and there are several messy groups of species like Mamenchisaurus and Omeisaurus that I'd like to have an opinion of. The format will be the same as the theropod parts, though I'm not sure how it will be integrated yet. This month I've been creating the backbone of each page by listing the named clades with their definitions, and once that's done I'll upload the extremely partial first version. None of this means I'll be ignoring theropods of course, as they remain my main interest. Expect me to switch back and forth between my sub-interests as usual.

For a sample, here's the current Ultrasaurus entry. The phylogenetic relationships will be considered further once I have a better framework to use.

Wednesday, March 2, 2011

Well, that was a sad month post-wise. But the good news is that I got my part of the manuscript finished, so now we'll see how the submission goes. Here's a post to finish the Zhao series, dealing with his ornithischians. No illustrations are known for the undescribed taxa, and the relationships and post-description data aren't discussed for the four officially described genera. Sorry about the small text size below and oddly different formatting for Monkonosaurus- Blogger's terrible when it comes to pasting things from Word. The text looks large and identical in the compose window...

Coming up, the rest of the "suggested phylogenetic definitions" series and a (perhaps not so-)surprise announcement of a new section for the Database I've been working on.

"Tianchungosaurus" Zhao, 1983Etymology- May have the same etymology as Dianchungosaurus, which refers to the Dianzhong Basin of Yunnan. Alternatively, Tianzhong would mean "in the fields", but the etymology remains uncertain since the name was not also written in Chinese by Zhao.Early Jurassic
China
Comments- Stated to be a pachycephalosaur, but Zhao includes heterodontosaurids and ceratopsians in this group too. He referred it to his new superfamily Tianchungosauroidea, supposedly ancestral to other marginocephalians and including Heterodontosaurus (which would make the superfamily Heterodontosauroidea instead). Lambert (1990) believed it may be a misspelling of Dianchungosaurus (then thought to be a heterodontosaurid, since identified as a mesoeucrocodylian), which was also followed by Olshevsky (1991) and The Paleobiology Database.

Dianchungosaurus? "elegans" Zhao, 1985Etymology- The species name means elegant.Hettangian, Early Jurassic
Zhangjiawa Member of the Lufeng Formation, Dianchung, Yunnan, China
Comments- Zhao (1985) stated this was a heterodontosaur, and that chaoyangsaurids evolved from it. Chure and McIntosh (1989) place this in Pachycephalosauridae and mark this name as sic, perhaps indicating they believe it to be intended as "Tianchungosaurus". Similarly, Olshevsky (1991) notes it may be the intended type species of that genus.

I've kept the above entries separate to better reflect what is known and has been said about each name. It seems probable "Tianchungosaurus" and Dianchungosaurus? "elegans" refer to the same material, since the other new Jurassic taxa listed by Zhao (1983) are also mentioned in his 1985 paper, both are heterodontosaurs from the Early Jurassic of China, and D and T are similar sounds. It also seems probable "Tianchungosaurus" is the misspelling, since Zhao did name additional species of other previously named genera (e.g. Megalosaurus, Plesiosaurus, Ichthyosaurus) and two heterodontosaurs having such similar names is unlikely. What's more uncertain is if "elegans" is actually a heterodontosaurid or is a crocodylian like the type species of Dianchungosaurus is now known to be. Perhaps it is best placed in Archosauria incertae sedis for now.

"Changdusaurus" Zhang et al., 1982"Changtusaurus" Zhao, 1983"Changdusaurus laminaplacodus" Zhao, 1985"Chendusaurus" Lambert, 1990"Chengdusaurus" Lambert, 1990"Changtusaurus laminaplacodus" Chure and McIntosh, 1989"Changduosaurus laminaplacodus" Fang, Zhang, Lu, Han, Zhao and Li, 2006Etymology- Changdu is a variant of Qamdo, the county the remains were found in. The species name refers to thin plates, presumably the dermal plates typical of stegosaurs. Middle Jurassic
Middle Dapuka Group, Dabuka, Qamdo County, Tibet, China
Material- (~7 m) specimen seemingly including dermal plates, and probably ischia and femoraComments- This was first announced by Zhang et al. (1982), who also gave its length. Zhao (1985) states that "transitional characters, as exemplified by the Middle Jurassic stegosaurs in Tibet" include flat ischia, a reduced fourth trochanter, and broad, thin dermal plates. These may thus be characteristics of "Changdusaurus". Lambert (1990) listed both "Chendusaurus" and "Chengdusaurus" as "perhaps Changdusaurus", but the original source of these variants is unknown. Glut (1997) incorrectly listed it as being Late Jurassic in age. Weishampel et al. (2004) list it as "undescribed ?stegosaur". Fang et al. (2006) indicated it derives from lower in the Dapuka Group than the other reported taxa. Based on the sequence of spellings, "Changdusaurus" is probably the intended one.Relationships- Stated by Zhao (1983) to be an intermediate stegosauroid, it has been assigned to Stegosauridae by later authors (e.g. Chure and McIntosh, 1989; Olshevsky, 1991). Thin plates are only known in the Loricatosaurus+Stegosaurus clade, so may indicate "Changdusaurus" is a member. All stegosaurs have reduced fourth trochanters, though those of stegosaurids are absent. Ischial thickness is not currently used in stegosaur phylogenetics. References- Zhang et al., 1982. The Roof of the World: Exploring the Mysteries of the Qinghai-Tibet Plateau. Harry N. Abrams Inc, New York. 227 pp.

Monkonosaurus lawulacus Zhao vide Dong, 1990
= "Monkonosaurus" Zhao, 1983
= "Monkonosaurus lawulacus" Zhao, 1986
= "Monkonosaurus lawulocus" Dong, 1987
= "Monkosaurus lawulacus" Chure and McIntosh, 1989Etymology- Monko is a variant of Markam, the county it was discovered in. Lawulashan is the mountain the material was discovered on.Early Cretaceous
Lura Formation, Laoran, Markam County, Tibet, China
Holotype- (IVPP coll.) (~5 m) two partial vertebrae (lost), sacrum (~311 mm), ilia (~905 mm), three dermal plates (lost)Comments- The holotype was discovered in 1976 by a team from the Chinese Academy of Sciences, and originally referred to Zhao's (1983) new thyreophoran ("armatosaurian") superfamily Oligosacralosauroidea, distinguished by its lower number of sacrals than ankylosaurids (3-5, and indeed Monkonosaurus has 5). The superfamily is invalid as there is no genus "Oligosacralosaurus", and Monkonosaurus has since been universally referred to Stegosauridae. The taxon was eventually officially described by Dong (1990), and the iliosacral block has been photographed by Dong (1987) and Dong (1990). Note Dong (1990) is incorrect that Zhao used a species name for the taxon in 1983. Maidment and Wei (2006) redescribed the material and refigured the now broken iliosacral block, believing the taxon to be indeterminate, a conclusion Maidment repeated in 2010. Glut (1997) incorrectly credits the official name to Zhao, 1983/6.References- Zhao, 1986. [unknown title] in Hao, Su, Yu and Li (eds.). The Cretaceous System of China. Stratigraphy of China. 12, 67-73.
Dong, 1987. Dinosaurs from China. Beijing: China Ocean Press. 114 pp.
Dong, 1990. Stegosaurs of Asia. in Carpenter and Currie (eds.). Dinosaur Systematics. Cambridge: Cambridge University Press. 255-268.
Maidment and Wei, 2006. A review of the Late Jurassic stegosaurs (Dinosauria, Stegosauria) from the People’s Republic of China. Geological Magazine. 143(5), 621-634.
Maidment, 2010. Stegosauria: A historical review of the body fossil record and phylogenetic relationships. Swiss Journal of Geosciences. 103, 199-210.

Polysacralosauroidea Zhao, 1983Comments- Zhao's name for Ankylosauria. Note it is invalid due the absence of a genus "Polysacralosaurus".